JP3129026B2 - Inspection method of cream solder printing condition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a printed state of a cream solder, which inspects a printed state of cream solder printed by a cream solder printing apparatus in the field of surface mounting.

[0002]

2. Description of the Related Art In recent years, mounting inspection apparatuses have been introduced as printed circuit boards have been increasingly mounted at high density and inspection and correction by humans have become difficult. In particular, since a bridge failure in the cream solder printing process is liable to be a bonding failure as it is, a cream solder printing inspection apparatus equipped with an inspection algorithm for determining the bridge failure has been developed.

[0003] An example of the above-mentioned conventional bridging fault determination algorithm will be described with reference to the drawings.

FIG. 7 is a flowchart of the conventional processing, and FIG. 8 is a conceptual diagram thereof. In FIG. 7, 26 is a measurement window setting step, 27 is a contour tracking processing step, 28 is a bridge width detection processing step, and 29 is a bridge failure determination processing step. 8th
In the figure, 30 is an inspection start land, 31 is a measurement window, 3
2 is a contour tracking start point, 33 is an intersection between the solder contour and the measurement window 31, 34 is a margin from the intersection 31, 35 is a lead pitch width, 36 is a bridge measurement window, and 37 is a minimum bridge width.

In a measurement window installation processing step 26, a measurement window 31 is installed on the inspection start land 30. Thereafter, in the contour tracking processing step, the measurement windows 3 are sequentially arranged from the contour tracking start point 32.
By tracing the outline of the solder in 1, an intersection 33 with the measurement window 31 is obtained. If the intersection 33 is not detected, it is determined to be normal. If the intersection point 31 is detected, the bridge width detection processing step has a margin width 34 and a lead pitch width 35.
Is set, and the minimum bridge width 37 in the window is measured. Thereafter, a comparison between the minimum bridge width 35 measured in the bridge failure determination processing step and the bridge determination width, that is,

[0006]

(Equation 1)

In this case, it is determined that the bridge is defective.

[0008]

However, in the above-described configuration, since the bridge judgment is performed for each land, the process is performed using a recent nitrogen reflow furnace.
A bridge of one land often breaks in the reflow furnace and becomes normal, and if the lands are continuously bridged, they do not always break and some of the lands become defective even after reflow. In other words, there is a problem that the bridge failure at the time of printing and the bridge failure after reflow do not easily match.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, there is provided a cream solder print inspection method which has a function of judging a bridge failure from the continuity of lands that bridge. The purpose is to:

[0010]

According to the present invention, particularly in a process using a nitrogen reflow furnace, a bridge failure of only one land during solder printing does not result in a failure after reflow, and a failure of a continuous land causes failure even after reflow. It becomes possible to cope with the phenomenon that is liable to occur.

[0011]

【Example】

(Embodiment 1) An algorithm for judging a bridge failure at the time of cream solder printing according to an embodiment of the present invention will be described below.

The inventors of the present invention have investigated the correlation between defective printing and defective bonding in a mounting process using a nitrogen reflow furnace, and have found the following.

In the case of a bridge at the time of printing, if there is only one land, it is likely to break during reflow, resulting in a good product. In the case of a bridge of continuous lands (5 to 10 lands), all bridges will break during reflow. Of these, one of them often causes poor bonding.

A description will now be given, with reference to the drawings, of an inspection algorithm having a function of judging bridge judgment at the time of printing from its continuity so that such a phenomenon can be inspected.

FIG. 1 is a flowchart of the processing in the first embodiment of the present invention, and FIG. 2 is an image diagram thereof. In FIG. 1, 1 is a contour tracking process, 2 is a moving distance land calculating process, 3 is a continuous bridge determination process, and 4 is a next inspection land moving process. In FIG. 2, 5 is an inspection start land, 6 is an outline tracing start point 7, 8 is an XY coordinate value at which the Y coordinate takes the maximum value among the coordinate values detected in the outline tracing processing step 1, and a Y coordinate. X takes the minimum value
Y coordinate value, 9 is land pitch width, 10 is next inspection land, 11 is inspection start land 5 which has been notified in advance.
Are the center coordinates of the next inspection land known in advance.

First, in the contour tracing processing step 1, solder contour tracing is sequentially performed from a solder contour tracing start point 6 on an arbitrary inspection start land 5 in the input image until the solder contour tracing returns to the start point 6. At this time, an XY coordinate value 7 (Xa, Xmax) at which the Y coordinate takes the maximum value and an XY coordinate value 8 (Xb, Ymin) at which the Y coordinate takes the minimum value are simultaneously obtained. Next, in the moving distance (land) calculation processing step, the XY coordinates 7, 8 and the land pitch width 9 were used.

[0017]

(Equation 2)

Then, how many land solders are tracked is calculated. Then, in the continuous bridge determination processing step 3, the number N of continuous bridge failure determination lands is compared with the value of (Equation 1).

[0019]

(Equation 3)

In the case of the above, a continuous bridge failure is determined. If all land inspections have not been completed, in the next inspection land movement processing step 4, the center of the inspection start land is added to the value of (Equation 1), and the land is moved to the next inspection land center position, and the contour tracking processing is performed. The same processing is performed from step 1.

(Embodiment 2) FIG. 3 is a flowchart of a process in a second embodiment of the present invention, and FIG. 4 is an image diagram thereof.

In FIG. 3, reference numeral 13 denotes a measurement window setting process,
14 is a bridge width detection process. In FIG. 4, 1
5 is an inspection start land, 16 is a measurement window, and 16 is a bridge measurement window.

First, in the measurement window setting processing step 13,
The first embodiment is applied only to the land where the bridge failure has occurred by the conventional method of detecting the bridge failure by installing the measurement window 16 and the bridge measurement window 16 in the bridge width detection processing step 14 for the inspection start land 15.

(Embodiment 3) FIG. 5 is a flowchart of a process in a third embodiment of the present invention, and FIG. 6 is an image diagram thereof. In FIG. 5, reference numeral 18 denotes a measurement window setting processing step,
Denotes a contour tracing processing step, 20 denotes a bridge width and area detection processing step, 21 denotes a data rearrangement processing step by land number for each lead direction, and 22 denotes a continuous bridge determination processing step.
In FIG. 6, reference numeral 23 denotes an inspection start land, 24 denotes a measurement window, and 25 denotes a bridge measurement window.

As in the conventional example, the measurement window setting step 18
The measurement window 24 is set, and after the contour tracking process step 19, the bridge measurement window 25 is set. Thereafter, in the bridge width / area detection processing step 20, the minimum bridge width d and the solder area measurement S in the bridge measurement window 25 are performed. When the above processing is completed for all lands, the data is rearranged in the data rearrangement processing step described above by land number for each read direction. Then, in the continuous bridge determination process, the total number N of the continuous lands and the bridge width of the continuous lands.

[0026]

[Outside 1]

Total area

[0028]

[Outside 2]

Is obtained and compared with each criterion value, for example,

[0030]

(Equation 4)

Then, a continuous bridge failure is determined.

[0032]

As described above, according to the present invention, the addition of a function of judging a bridge defect at the time of cream solder printing from the continuity thereof enables one-time judgment of a process using a nitrogen reflow furnace. Although a bridge is unlikely to cause a bonding failure, a continuous number of bridges can easily cope with a phenomenon that a bonding failure is likely to occur somewhere, and the line-out rate in print inspection can be reduced.

[Brief description of the drawings]

FIG. 1 is a processing flowchart of a first embodiment of the present invention.

FIG. 2 is a plan view of a land showing a processing image of the first embodiment of the present invention.

FIG. 3 is a processing flowchart of a second embodiment of the present invention.

FIG. 4 is a plan view of a land showing a processing image.

FIG. 5 is a processing flowchart of a third embodiment of the present invention.

FIG. 6 is a plan view of a land showing a processing image.

FIG. 7 is a processing flowchart of a conventional example.

FIG. 8 is a plan view of a land showing a processing image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Contour tracking processing step 2 Moving distance (land) calculation processing step 3 Continuous bridge determination processing step 4 Next inspection land moving processing step 5 Inspection start land 6 Contour tracking start point 7 XY of solder contour part whose Y coordinate value is the maximum value Coordinates 8 XY coordinates of solder outline where Y coordinate value is minimum value 9 Land pitch width 10 Secondary inspection land 11 Center coordinates of inspection start land 12 Central coordinates of secondary inspection land 13 Measurement window installation processing 14 Bridge width detection processing 15 Inspection Start land 16 Measurement window 17 Bridge width measurement window 18 Measurement window installation processing step 19 Contour tracking processing step 20 Bridge width and area detection processing step 21 Data rearrangement processing step by land number by lead direction 22 Continuous bridge determination processing step 23 Inspection start land 24 Measurement window 25 Bridge measurement window 26 Measurement window installation processing process 27 Outline tracking Step 29 bridging determination process 30 inspection start land 31 measuring window 32 contour intersection 34 margin width 35 land pitch of the measuring window tracking start point 33 solder contour 36 bridge measuring window 37 minimum bridge width

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/958 G06T 1/00 G06T 7/00 H05K 3 / 32-3/34 512

Claims (3)

(57) [Claims] 1. An image input processing step of inputting an image by an image pickup means and storing the image in an image storage means in order to inspect a continuous continuous bridge failure over many lands which is likely to occur in a leaded electronic component or the like at the time of cream solder printing. A first step of sequentially tracing the contours of the cream solder, a second step of calculating the movement distance in the first step, and a third step of determining a continuous bridge failure by comparing the result of the second step with a determination value.
And a fourth step of moving to the next inspection object based on the result of the second step. 2. A fifth step in which a measurement window is set before the first step, a sixth step in which the contour of the cream solder in the measurement window set in the fifth step is sequentially tracked, and According to the result, a seventh step of setting a bridge measurement window and measuring a bridge width and an eighth step of determining a single land bridge failure by comparing a result of the seventh step with a determination value are performed. Item 1. The method for inspecting a cream solder printing state according to Item 1. 3. A first step of setting a measurement window after a processing step of performing an image input by an image pickup unit and storing the image in an image storage unit in the inspection of a continuous bridge failure during cream solder printing. A second step of sequentially tracing the contour of the cream solder in the measurement window set in the step,
Based on the results of the process, install a bridge measurement window and set the bridge width,
A third step of measuring the solder area in the bridge measurement window;
These are the fourth step of determining a single land bridge failure by comparing the result of the step with the determination value, the fifth step of rearranging the results of the fourth step by land number, and the result of the fifth step. The sixth step of determining a continuous bridge by comparing the number of continuous land numbers, the sum of bridge widths in the continuous lands, and the sum of areas in the bridge measurement window with each determination value. Inspection method for the printed condition of cream solder.